This is the first part of a two part story which forms the finale of series 2 which was David Tennant's first season as the 10th Doctor. The story is that 10 and Rose arrive in London to find the population of the world, including Rose's mum Jackie have all become convinced their dead relatives and friends are visiting them as ghosts. Torchwood, an organisation set up following the Doctor's encounter with Queen Victoria on the Torchwood estate (in the episode Tooth and Claw) is facilitating these encounters which utilise a tear between this reality and a parallel universe which turns out to be the alternative Earth the Doctor and Rose visited earlier in the series (Rise of the Cybermen and The Age of Steel) where they battled Cybermen and where they left Rose's boyfriend Mickey. The Doctor investigates and it turns out to be far more sinister than Torchwood or anyone understands, the Cybermen are breaking through from the parallel universe. In addition there is a very strange alien vessel being kept at Torchwood which has a dark secret. It unleashes the Daleks from the void in an awesome end to part one of the story.

The way this story links in elements from part stories and brings things to a hugely dramatic and satisfying climactic pair of episodes is brilliant. Russell T. Davies has done a magnificent job weaving all the elements into such an excellent story which is complex but still makes sense and is thoroughly great quality. This is exciting, entertaining and beautifully executed. Over the 2 episodes there is great humour, great thrills and some very moving drama as Rose gets separated from the Doctor. The acting, the writing, the effects and the action are all top notch. This is up with the best of the great history of Doctor Who. One of my top 30 ever stories.

This second part of the story has the huge fun of seeing Cybermen versus Daleks. An epic.